The Study on the Removal of Chromium in the Chrome Tanned Leather Waste by Acid Extraction Method
Date Issued
2004
Date
2004
Author(s)
Hsu, Chih-Hsien
DOI
zh-TW
Abstract
The major solid wastes generated of leather processing are including leather powders, leather sweeps, and leather shavings. The additive chromate in the leather process still remains in the leather waste. According to study results, one ton of wet salted hides yield only 200 kg of leather but over 600 kg of solid waste, along with about 250 kg of tanned solid waste. The total chromium of leather waste is higher than 15,000 mg/kg, and the TCLP value of Cr is higher than regulated limit of hazardous industrial waste. According to the EPA data in 2002, the amount of leather waste is about 37,000 ton. If we can find some good method to make leather waste transferring to valuable by-products, a lot of problem of waste will be solved.
The results of experiment show that the total chromium of leather waste, which wasn’t cooked with high-pressure steam, can be extracted easier. The liquid to solid ratio (L/S) doesn’t have significant effect of extraction efficiency. Nitric acid is the best extracts in inorganic acids, and oxalic acid is the best extracts in organic acids. We can obtain high extraction efficiency when extracts made by high concentration. If the concentration of extracts was too high, leather waste will be completely soluble in extracts and can’t reuse in composting way by solid shape. We can obtain high extraction efficiency when the extraction time was long. The max concentration of extracts will be found when the extraction was lasting for a period of time. It will be a waste of time and lower extraction efficiency when the extraction time was too long. The max extraction efficiency of nitric acid extracts is 54.35% when the concentration is 1.75N and the extraction time is 6hr at 40℃. The max extraction efficiency of oxalic acid extracts is 81.24% when the concentration is 1.5N and the extraction time is 36hr at room temperature. It will spend fewer time when the nitric acid extracts was extracting at high temperature, but leather waste will be completely soluble in extracts when the extraction time more than 6hr and the extraction temperature more than 45℃. The total extraction efficiency of two-step extraction is 96.82%, when the first step is 0.25N oxalic acid extracting for 24hr and the second step is 0.25N sodium chloride extracting for 24hr. The extraction efficiency of the mixed extracts made by 0.25N oxalic acid and 1.75N nitric acid in 1:1 volume ratio is 95.47% when the extraction time is 48hr. The 200mL 1.25N nitric acid extracts will be precipitation when 20mL 15N sodium hydroxide solution was added and it can removal 96.76% of chromium. The total chromium of the leather waste, which was treated by the best dechroming efficiency 96.82% in this experiment, is 550mg/kg. The adding ratio can be 27% when we make compost by leather waste. Comparing with the adding ratio of the leather waste, which wasn’t treated, the number of the adding ratio can enhance 30 times.
Subjects
廢皮革
鉻鞣
酸萃取
l eather waste
chrome tanned
acid extraction method
SDGs
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-93-R89541106-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):164b3a4e455875c57d48c5d6142a80d4